This invention relates to an ignition time control device for a multicylinder internal combustion engine.
Heretofore, a vacuum advancer or a centrifugal advancer enclosed in the distributor and connected mechanically with the engine has been used for ignition time control for this type of engine. However, in order to meet the increasing demand for reduction of fuel consumption and regulations against emission, such mechanical control is insufficient in point of precision and temporal changes of the components and electronic control is thought to be indispensable.
In such electronic control, it is customary to compute the optimum ignition time with the output signal from a reference position sensor in the distributor as one input and the output signal from a sensor sensing the operating conditions of the engine, such as negative pressure in the suction manifold, as another input and to interrupt the primary current of the ignition coil in accordance with the computed timing to control the ignition timing. In this instance, the high voltage induced in the secondary side of the ignition coil is distributed to each engine cylinder by the high voltage distributing system of the similar to a conventional system. Thus the distributor is still required for high voltage distribution, although the mechanical advancer is no longer required.
In order to obiate such problem, it has been proposed to control the ignition timing by a low voltage distributing system which replaces the high voltage system making use of the distributor.